Pneumatic tires often desirably have indicial markings, such as trademarks or other markings. These indicia typically are formed directly into the rubber sidewall during the tire molding process. Thus, the indicia may be raised lettering or other shapes, and may be colored with white pigments or other colorants in the rubber compound.
White sidewall tires are very popular with car makers. Tires having other types of appliques on the sidewalls thereof, such as lettering, logos, decals, or bar codes and the like, are also very popular. However, the construction of tires having white sidewalls or decorative appliques on the sidewall thereof is a complicated procedure. It generally involves the co-extrusion of a black sidewall rubber with a white sidewall rubber and laminating a protective cover strip over the white rubber to form a sidewall preassembly. This tire sidewall preassembly is then applied in sequence with the other required tire components to the tire building drum to form a green or uncured tire. The green tire is then typically cured in a tire press, with the desired applique being formed by the grooves in the tire mold. After the tire has been cured, it is carefully ground and buffed to expose the decorative applique which was previously covered and protected by the cover strip.
Co-extrusion is a complicated process which involves the utilization of sophisticated equipment and a large number of profile dies. The grinding and buffing step which is required to remove the cover strip is also complicated and labor intensive. These additional steps, which are required in building tires having decorative appliques on a sidewall thereof, adds significantly to the cost of building the tire.
In conventional white sidewall tires, the white rubber component represents a very substantial portion of the sidewall. However, it is desirable for tires to have thin sidewalls in order to attain desired performance characteristics. Accordingly, the decorative applique on the sidewall of a tire should be as thin as possible. Nevertheless, certain production and performance criteria has limited the degree to which the thickness of sidewall applique can be reduced.
There are additional problems associated with tires having decorative applique on a sidewall thereof which are built using standard techniques. For instance, such tires have more blemishes, imperfections, and voids in the sidewall area as compared to black sidewall tires. Additionally, problems associated with the white sidewall splice opening sometimes also occur. Misalignment of the white sidewall preassembly relative to mold grooves is a frequently-encountered problem which leads to blemished tires. The grinding procedure used in building standard tires having decorative appliques on a sidewall thereof sometimes leads to the formation of surface crack sites.
For the aforementioned reasons, tire having decorative appliques on a sidewall thereof and the conventional procedures used in building such tires leave much to be desired. To obviate these shortcomings associated with standard techniques for building tires having decorative appliques on a sidewall thereof, it has been proposed to replace the previously known sidewall decorative features with appliques which are painted on to conventional black wall tires. However, painting designs on to the sidewall of tires has not proven to be a satisfactory answer to the problem. This is largely due to the fact that designs which are painted on are quite thin and can be easily damaged by scraping, scuffing and the like.
The concept of applying premolded tire sidewall appliques to standard black wall tires has also been proposed. Difficulties have been encountered with maintaining adequate adhesion between the sidewall applique and the tire. Also, tires made utilizing such techniques typically have inferior scuff resistance such that the applique fails at the interface.
It is sometimes desired to apply indicia directly to an already molded and cured tire, typically on the sidewall area. To do this, various coatings and paints have been used to form indicia. However, poor adhesion or durability of the coatings usually leads to unacceptable performance of this type of indicia.
It would, therefore, be desirable to have a tire with indicia applied to a cured tire sidewall surface, wherein the indicial coating material offers good adhesion and durability.